Minor VARIABLE_SPINDLE feature toggle refactoring (#16)

* Modify code CSV format.

- Wrap value in quotes to avoid issue with embedded commas. This occurs
  in one of the alarm codes.

- Change header row format to allow same parsing code as data rows.

* VARIABLE_SPINDLE feature flag experiment.

- Use a macro for 'spindle_set_speed' and 'spindle_sync' to reduce the
  number of required VARIABLE_SPINDLE checks.

grbl/spindle_control.h

@@ -57,10 +57,12 @@ uint8_t spindle_get_state();
 #else
   
   // Called by g-code parser when setting spindle state and requires a buffer sync.
-  void spindle_sync(uint8_t state);
+  #define spindle_sync(state, rpm) _spindle_sync(state)
+  void _spindle_sync(uint8_t state);
 
   // Sets spindle running state with direction and enable.
-  void spindle_set_state(uint8_t state);
+  #define spindle_set_state(state, rpm) _spindle_set_state(state)
+  void _spindle_set_state(uint8_t state);
 
 #endif